The present invention relates to a new and improved construction of a controlled deflection roll.
In its more particular aspects, the present invention relates to a new and improved construction of controlled deflection roll comprising a stationary or non-rotating roll support member or beam and a roll shell which is rotatable about the stationary roll support member and which is supported at the stationary roll support member by means of hydraulic support or pressure elements. The roll shell defines an outer roll shell surface and there is provided in the interior space of the roll shell a predetermined number of traveling rings each of which is associated with a related one of the support elements. The inner traveling ring surface of each one of the traveling rings provides a travel path for the related support element.
Controlled deflection rollers of the classical type as described, for example, in U.S. Pat. No. 3,885,283, granted May 27, 1975, and U.S. Pat. No. 3,802,044, granted Apr. 9, 1974, are used to roll band-shaped materials, for example, metal bands, like aluminum foils or steel sheet material, paper webs or similar materials.
In the arrangement as described, for example, in U.S. Pat. No. 3,921,514, granted Nov. 25, 1975, the controlled deflection roll cooperates with a counter roll and the contact or pressing force by means of which the two rollers are pressed against each other along a pressure or pressing line is generated by the pressure of a pressure fluid supplied to hydrostatic support elements. The use of controlled deflection rolls in such arrangement affords the advantage that the outer surface thereof adapts itself to the shape of the counter roll along the pressure or pressing line and follows any deformation of the counter roll. Furthermore, the contact or pressing force acting along the pressure or pressing line can be individually controlled and regulated by suitably adjusting the pressure of the pressure fluid effective at the individual hydrostatic support elements in accordance with a desired contact or pressing force profile along the pressure or pressing line, i.e. in axial direction of the rolls.
In order to ensure a desired surface quality of the rolled material, for example, of aluminum foils, steel bands or paper webs, the controlled deflection roll must be provided with a solid and sufficiently smooth outer surface. Preferably, therefore, roll shells made of a suitable type of steel are used in such controlled deflection rolls. Additionally, and in order to achieve the desired effect, the roll shell must have sufficient flexibility in lengthwise as well as in circumferential direction and the material as well as the wall thickness of the roll shell of the controlled deflection roll must be correspondingly selected. As a matter of fact, a small wall thickness would be advantageous with respect to a good transverse flexibility, i.e. a deformability of the roll shell transversely to the pressure or pressing line or to the axis thereof. However, due to the partially significant forces exerted by the support elements, the deformation of the roll shell in circumferential direction would become so large that the yield strength or elastic limit of the material can be reached. Therefore, the wall thickness of the roll shell may not fall short of a predetermined value in order to preclude any undue deformations.
In the known controlled deflection rolls in which the support elements directly act upon the inner surface of the roll shell it is, therefore, impossible to achieve optimum flexibility of the roll shell transversely to the pressure or pressing line as well as in circumferential direction and a compromise must be made with respect to the wall thickness of the roll shell. The roll shell thus can not be selected with any desired thinness in consideration of maintaining sufficient circumferential stability. Consequently, a variation in the contact or pressing force at the location of one support element becomes effective at the adjacent support elements due to the inherently prevailing longitudinal stiffness of the roll shell. A predetermined desired contact or pressing force profile, therefore, can not be adjusted and regulated sufficiently precisely for many kinds of applications at the necessarily required high wall thicknesses and the line force can not be varied sufficiently precisely at the desired locations. There are further required, for the deformation of a roll shell having great wall thickness, a considerable force and a correspondingly greater amount of input power.
A controlled deflection roll as known, for example, from U.S. Pat. No. 4,058,877, granted Nov. 22, 1977, and from German Pat. No. 1,155,750, granted Oct. 17, 1963, comprises a thin elastic roll shell at the inner surface of which traveling rings are provided which are fixedly connected to the roll shell and synchronously rotate conjointly with the roll shell. The traveling rings form travel paths for related hydrostatic support elements or anti-friction or roller bearings hydrostatically pressed thereagainst.
The use of such features in rolls having a hard surface as required, for example, for the rolling of metal foils, i.e. providing traveling rings which are fixedly connected to and rotate conjointly with the roll shell, however, would not eliminate the prior art disadvantages mentioned hereinbefore because the deformation in circumferential direction would remain unchanged, and thus, also the danger of undesirably reaching the yield strength or elastic limit as well as the need for a greater force.